Apparatus for the simultaneous casting of multipropellant solid fuel rocket motors



June 24, 1969 w. c. ANDRl-:PoN-r 3,451,104

APPARATUS FOR THE SIMULTANEOUS CASTING OF MULTIPROPELLANT SOLID FUEL ROCKET MOTORS Filed Sept. 23, 1966 Sheet T R. www we c: MEM

June 24, 1969 w. c. ANDREPQNT 3,451,104

APPARATUS FOR THE SIMULTANEOUS CASTING OF MULTIPROPELLANT SOLID FUEL ROCKET MOTORS Filed sept. 25, 196e sheet ,3 of 2 INVENTOR. W/L BLU? 61 Am/PfSDa/vr BY n U.S. Cl. 18-26 3 Claims ABSTRACT OF THE DISCLOSURE An apparatus for the simultaneous casting of an uncured, multipropellant, solid rocket fuel. The apparatus comprises a mandrel means positioned within and extending along the central longitudinal axis of a rocket motor case together with baille means positioned within said motor case for separating the individual propellants of a multipropellant fuel.

The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to an apparatus for the casting of solid rocket fuels and, more particularly, to an improved technique for the simultaneous casting of multipropellant solid fuel rocket motors.

In the manufacture of rocket propellants, various methods are utilized for preparing the propellant materials. One method involves the illling of the rocket combustion chamber with an uncured propellant mixture, followed by an appropriate curing and finishing process. The rocket chamber itself is used as the mold for the propellant grain. The propellant may be added to the chamber in several ways. It can be introduced through a long tube or bayonet which is lowered into the chamber, or a vacuum casting technique can be employed. Either of the methods referred to above are conventional and have proved satisfactory. However, the casting of multipropellant grains presents a disadvantage since such grains must 'be cast separately in order to provide a proper bond at the interface between the individual propellants of the multipropellant fuel. The use of separate casting technique involves increased labor with its attendant increase in cost.

In accordance with this invention, however, it has been found that the problems encountered in casting multipropellant solid rocket fuels according to prior art techniques can be abrogated by positioning a circumferential baille, concentrically within the combuston chamber. The baille is positioned at the desired interface between the individual propellants in order to maintain a separated relationship. Two or more propellants may be cast simultaneously. The baille is of suilicient length to prevent propellant mixing or splashing. The propellants are cast simultaneously until a sufficient head is reached to cause the propellants to flow together as the lbaille is raised. The level of the propellants should be kept approximately the same on both sides of the baille. The baille is slowly raised by appropriate means such as cables to permit additional casting of the propellants. This operation is continued until the desired grain length is reached. The baille is then removed slowly. The shape of the circumferential baille could range from a cylindrical shape to a star shape. The baille may be employed with either of the conventional bayonet or vacuum casting apparatus of the prior art.

Accordingly, it is the primary object of this invention to provide an apparatus for the simultaneous casting of a multipropellant rocket fuel.

rCC

Another object of this invention is to provide a Ibaille means between the separate propellants of a multipropellant grain prior to casting the multipropellant fuel.

A further object of this invention is to provide a rocket fuel casting apparatus having a circumferential baille means adapted to be withdrawn from the apparatus.

Still a further object of this invention is to provide an apparatus which permits the simultaneous casting of multipropellant rocket feuls in an eillcient and economic manner.

The above and still further objects, advantages and features of this invention will become readily apparent upon consideration of the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a sectional view of a motor case showing the circumferential baille means of this invention utilized in a bayonet-type casting operation; and

FIGURE 2 is a sectional view of a motor case segment showing the circumferential baille means of this invention utilized in a vacuum-type casting operation.

Referring more in detail to the drawings wherein like parts are designated by like reference numerals, the reference numeral 10 is used to designate a portion of a motor case for a solid propellant rocket motor. The motor case A10 forms no part of the invention and is used only to show the apparatus embodying the invention when used in the casting of an uncured multipropellant comprising separate propellants A and B.

The apparatus embodying the invention comprises a circumferential baie 12 that is provided with a plurality of lifting eyes 14 on one end of the baille 12 that are engaged by lifting hooks connected to hoist cables 16. A mandrel 18 extends the length of the motor case 10. One end 20 of the mandrel 18 extends through a ilanged igniter opening 22 in the head end 24 of the motor case 10, to rest on a cap 26 that is iitted to the flanged opening 22 with an airtight seal as shown in FIG. 1. With the mandrel 20 in place and the baille 12 in a lowered position as shown at 28, the apparatus is ready for use. Separate propellants A and B are simultaneously cast into the motor case, either by means of bayonet tubes 30 and 32, as shown in FIG. 1, or by illling means 34 and 36, as shown in FIG. 2. As the two distinct propellants A and B are cast into the motor case, the baille 12 is slowly raised by means of hoisting cables 16 until a suflcient head is reached to cause the propellants A and B to ilow together. The level of the separate propellants A and B should be maintained approximately the same on both sides of the baille 12. In order to facilitate even illling, FIG. 1 shows the use of a plurality of bayonet tubes. However, a single bayonet tube for each propellant could be utilized if desired. The casting operation is continued until the desired grain length is obtained, at which time the baille 12 is slowly withdrawn from the motor case 10.

Slowly lifting the baille 12 separates the propellants during the casting operation. The concept of this invention eliminates the need and expense of two propellant mandrels, thereby reducing the processing labor to that of a single propellant grain. This invention also provides for a better multipropellant bond since the bond is completed prior to curing the propellants.

Rocket motor performance requirements are becoming more and more demanding with higher performance rockets employed. Multipropellant rocket grains increase volumetric loading and mass fraction and allow the use of toxic propellants in the outside grain of the iirst stages and is applicable to multithrust level rocket motor requirements.

It will be seen, therefore, that this invention provides a means for improving the production of multipropellant grains in a more eilicient and economic manner, thereby 3 permitting an increased use of such grains in present day rocket motors.

It is believed that the foregoing description of the casting apparatus of this invention will be clear to those skilled in the art. However, it is to be understood that various changes and modifications can be made in the construction and arrangement of parts of the apparatus without departing from the spirit and scope of the invention and that all such changes as fall within the scope of the appended claims are intended to be included herein.

What is claimed is:

1. An apparatus for use in the simultaneous casting of an uncured multipropellant rocket fuel in the symmetrical motor case of a solid propellant rocket motor comprising a mandrel means for forming a core, said mandrel means extending the length of the motor case and positioned along the central longitudinal axis thereof, a tubular baie means surrounding said mandrel means and positioned within the motor case, said bale means being coaxially arranged in spaced relationship with respect to said case and mandrel means for separating the individual propellants of the said multipropellant rocket fuel, and hoisting 4 means connected to said bai-lle for slowly withdrawing said baflle from said motor case such that the interface between the separate propellants, formerly separated by said baffle, achieves a bond prior to curing.

2. An apparatus as dened in claim 1, including separate lling means located on each side of said baffle for casting the separate propellants of a multipropellant rocket fuel.

3. An apparatus as defined in claim 1, wherein said casing, mandrel and bafHe means are circular in cross section.

References Cited UNITED STATES PATENTS 965,150 7/1910 Atterbury. 1,030,480 6/ 1912 Packard. 3,186,035 6/ 1965 Grace. 3,261,891 7/1966` Craig.

I. HOWARD FLINT, JR., Primary Examiner.

U.S. Cl. X.R. 264--3 

